US3805185A - Switching oscillator controlled by a moving metal piece - Google Patents

Switching oscillator controlled by a moving metal piece Download PDF

Info

Publication number
US3805185A
US3805185A US00373969A US37396973A US3805185A US 3805185 A US3805185 A US 3805185A US 00373969 A US00373969 A US 00373969A US 37396973 A US37396973 A US 37396973A US 3805185 A US3805185 A US 3805185A
Authority
US
United States
Prior art keywords
oscillation
source
transistor
winding
circuit
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired - Lifetime
Application number
US00373969A
Other languages
English (en)
Inventor
Y Kishi
T Okamoto
K Kobayashi
M Yamaguchi
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Stanley Electric Co Ltd
Original Assignee
Stanley Electric Co Ltd
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Priority claimed from JP6671472A external-priority patent/JPS4926759A/ja
Priority claimed from JP6671572A external-priority patent/JPS5141227B2/ja
Priority claimed from JP6671672A external-priority patent/JPS5211742B2/ja
Priority claimed from JP6671372A external-priority patent/JPS4925846A/ja
Application filed by Stanley Electric Co Ltd filed Critical Stanley Electric Co Ltd
Application granted granted Critical
Publication of US3805185A publication Critical patent/US3805185A/en
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

Links

Images

Classifications

    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03K—PULSE TECHNIQUE
    • H03K17/00—Electronic switching or gating, i.e. not by contact-making and –breaking
    • H03K17/94—Electronic switching or gating, i.e. not by contact-making and –breaking characterised by the way in which the control signals are generated
    • H03K17/945—Proximity switches
    • H03K17/95—Proximity switches using a magnetic detector
    • H03K17/952—Proximity switches using a magnetic detector using inductive coils
    • H03K17/9537—Proximity switches using a magnetic detector using inductive coils in a resonant circuit
    • H03K17/9542—Proximity switches using a magnetic detector using inductive coils in a resonant circuit forming part of an oscillator
    • H03K17/9547—Proximity switches using a magnetic detector using inductive coils in a resonant circuit forming part of an oscillator with variable amplitude
    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03B—GENERATION OF OSCILLATIONS, DIRECTLY OR BY FREQUENCY-CHANGING, BY CIRCUITS EMPLOYING ACTIVE ELEMENTS WHICH OPERATE IN A NON-SWITCHING MANNER; GENERATION OF NOISE BY SUCH CIRCUITS
    • H03B5/00—Generation of oscillations using amplifier with regenerative feedback from output to input
    • H03B5/08—Generation of oscillations using amplifier with regenerative feedback from output to input with frequency-determining element comprising lumped inductance and capacitance
    • H03B5/12—Generation of oscillations using amplifier with regenerative feedback from output to input with frequency-determining element comprising lumped inductance and capacitance active element in amplifier being semiconductor device
    • H03B5/1203—Generation of oscillations using amplifier with regenerative feedback from output to input with frequency-determining element comprising lumped inductance and capacitance active element in amplifier being semiconductor device the amplifier being a single transistor
    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03B—GENERATION OF OSCILLATIONS, DIRECTLY OR BY FREQUENCY-CHANGING, BY CIRCUITS EMPLOYING ACTIVE ELEMENTS WHICH OPERATE IN A NON-SWITCHING MANNER; GENERATION OF NOISE BY SUCH CIRCUITS
    • H03B5/00—Generation of oscillations using amplifier with regenerative feedback from output to input
    • H03B5/08—Generation of oscillations using amplifier with regenerative feedback from output to input with frequency-determining element comprising lumped inductance and capacitance
    • H03B5/12—Generation of oscillations using amplifier with regenerative feedback from output to input with frequency-determining element comprising lumped inductance and capacitance active element in amplifier being semiconductor device
    • H03B5/1231—Generation of oscillations using amplifier with regenerative feedback from output to input with frequency-determining element comprising lumped inductance and capacitance active element in amplifier being semiconductor device the amplifier comprising one or more bipolar transistors
    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03B—GENERATION OF OSCILLATIONS, DIRECTLY OR BY FREQUENCY-CHANGING, BY CIRCUITS EMPLOYING ACTIVE ELEMENTS WHICH OPERATE IN A NON-SWITCHING MANNER; GENERATION OF NOISE BY SUCH CIRCUITS
    • H03B5/00—Generation of oscillations using amplifier with regenerative feedback from output to input
    • H03B5/08—Generation of oscillations using amplifier with regenerative feedback from output to input with frequency-determining element comprising lumped inductance and capacitance
    • H03B5/12—Generation of oscillations using amplifier with regenerative feedback from output to input with frequency-determining element comprising lumped inductance and capacitance active element in amplifier being semiconductor device
    • H03B5/1296—Generation of oscillations using amplifier with regenerative feedback from output to input with frequency-determining element comprising lumped inductance and capacitance active element in amplifier being semiconductor device the feedback circuit comprising a transformer
    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03K—PULSE TECHNIQUE
    • H03K17/00—Electronic switching or gating, i.e. not by contact-making and –breaking
    • H03K17/14—Modifications for compensating variations of physical values, e.g. of temperature
    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03B—GENERATION OF OSCILLATIONS, DIRECTLY OR BY FREQUENCY-CHANGING, BY CIRCUITS EMPLOYING ACTIVE ELEMENTS WHICH OPERATE IN A NON-SWITCHING MANNER; GENERATION OF NOISE BY SUCH CIRCUITS
    • H03B5/00—Generation of oscillations using amplifier with regenerative feedback from output to input
    • H03B5/02—Details
    • H03B5/04—Modifications of generator to compensate for variations in physical values, e.g. power supply, load, temperature

Definitions

  • the center tap of the two parts of the winding is connected to a DC source, a first parallel circuit comprising an oscillation transistor, and a bias circuit; and the opposite ends of the coils are connected across the oscillation transistor and DC source so that the degree of inductive coupling between the coils as controlled by the penetration distance of the metal piece between the coils produces abrupt start and cessation of oscillations in the circuit and corresponding changes in circuit current.
  • Temperature induced hysteresis fluctuations are compensated by use of a temperature responsive bias resistor, an oscillation winding core with a temperatureresponsive permeability characteristic, or bimetal fluxshunting strips adjacent to the oscillation windings.
  • This invention relates to a switching oscillator utilizing a fact that the output of an oscillator associated with an oscillation winding varies in response to the insertion or withdrawal of a metal piece into or from the oscillation winding, and the application of the switching oscillator to a proximity switch.
  • a proximity switch employing an oscillator has usually been used for the detection of a predetermined number of revolutions of a rotary member or for the detection of the position of a moving member, in addition to speed alarms of various vehicles.
  • the output from the oscillator undergoes a substantially linear change in response to the amount of movement of the metal piece combined with an object to be detected.
  • a switching circuit such as a Schmitt trigger circuit, which operates at a constant threshold value.
  • a detecting device including the oscillator and a detector and a switching unit including the Schmitt trigger circuit
  • a power source and an indicator are spaced apart from one other, three-wire coupling thereamong is required. Accordingly, the conventional circuit is complicated in construction and expensive, and its circuit characteristics are likely to vary with changes of temperature, voltage and like conditions. Moreover, there is the possibility that the circuit breaks down in the case of half-conduction of the oscillation transistor employed in the oscillator.
  • An object of this invention is to provide a switching oscillator capable of switching the output thereof in response to the movement of a metal piece to be detected.
  • Another object of this invention is to provide a proximity switch usingthe switching oscillator capable of extending by use of two-wire connection lines.
  • Another object of this invention is to provide a proximity switch using the switching oscillator substantially compensated against fluctuations of the hysteresis characteristic.
  • Further object of this invention is to provide a proximity switch using the switching oscillator substantially compensated against fluctuations of the switching characteristic within a certain temperature range.
  • a switching oscillator comprises an oscillation winding with a middle tap, a metal piece employed for being inserted into the oscillation winding to change the degree of coupling between first and second parts of the oscil lation winding divided thereinto at the middle tap, a first parallel circuit formed by the first part of the oscillation winding and a first resistor, a DC source, an oscillator transistor having its emitter-collector path connected.
  • the middle tap being connected to the first terminal of the DC source connected to the first parallel circuit, a first capacitor connected between the other end of thesecond part of the oscillation winding and the base of the transistor, bias means connected between the first terminal of the DC source and the base of the oscillation transistor, and a second parallel circuit formed by a second capacitor and a diode and connected between the base of the oscillation transistor and the second terminal of the DC source.
  • FIG. 1 is a circuit diagram illustrating an embodiment of this invention
  • FIGS. 2A and 2B are waveform diagrams explanatory of the operations of the embodiment shown in FIG. 1;
  • FIGS. 3 and 4 are characteristic diagrams explanatory of the characteristics of the embodiment shown in FIG. 1;
  • FIG. 5 is a circuit diagram illustrating another embodiment of this invention.
  • FIG. 6 is a circuit diagram illustrating a modification of a part of the embodiment shown in FIG. 5;
  • FIGS. 7 and 8 are characteristic diagrams explanatory of the characteristics of the embodiments shown in FIGS. 1 and 5;
  • FIGS. 9A, 10A and 11A are circuit diagrams illustrating an improved resistance circuit employed in this invention.
  • FIGS. 98, 10B and 11B are characteristic diagrams explanatory of the characteristics of the circuits shown in FIGS. 9A, 10A and 11A, respectively;
  • FIGS. 12 and 13 are respectively a perspective view and a longitudinal section illustrating examples of oscillation coils employed in this invention.
  • FIG. 14 is a characteristic diagram explanatory of the temperature characteristic of the coils shown in FIGS. 12 and 13;
  • FIG. 15 is a characteristic diagram explanatory of improved characteristics of the proximity switch of this invention using the coil shown in FIG. 13;
  • FIGS. 16A and 16B are perspective views illustrating improved examples of the oscillation coils employed in this invention.
  • FIG. 17 is a characteristic diagram explanatory of im* proved characteristics of a proximity switch of this invention using the coils shown in FIGS. 16A and 16B;
  • FIGS. 18A, 19A and 20A are circuit diagrams illustrating examples of a resistance circuit employed in this invention to improve the temperature characteristic of the proximity switch of this invention
  • FIGS. 18B, 19B and 20B are characteristic diagrams explanatory of characteristics of the circuits shown in FIGS. 18A, 19A and ZIIArespectively:
  • FIG. 21 is a characteristic diagram explanatory of improved characteristics of a proximity switch of this invention using the circuits shown in FIGS. 18A, 19A and 20A.
  • an oscillation winding 1 is divided at its middle tap linto first and second coils l-l and l-2.
  • a metal piece 2 moves in the direction of anarrow A, to alter the degree of coupling between the first and second coils 1-1 and l-2 of the oscillation coil 1.
  • a reference character 3 indicates a DC source, which has terminals 3 and 3
  • a first parallel circuit formed by the first coil 1-1 of the oscillation winding 1 and a resistor 4 is connected in series with the collector-emitter path of an oscillating NPN-type transistor 5 and connected between the terminals 3 and 3 of the DC source 3.
  • the middle tap l-0 of the oscillation winding 1 is connected to the terminal 3 of the DC source 3, and a first capacitor 6 is connected between the other end of the second coil l-2 of the oscillation winding 1 and the base of the oscillating transistor 5.
  • a bias resistor 8 Between the first terminal 3 of the DC source 3 and the base of the oscillating transistor 5 is connected a bias resistor 8.
  • the current flowing in the base of the transistor 5 through the coil l-2 and the capacitor 6 is increased, which provides an oscillation in a substantially saturated condition simultaneously with the initiation of the oscillation of the circuit.
  • This mode of operation is clearly shown in FIGS. 3 and 4, in which the relationships of the current i flowing in the circuit to the distance d of insertion of the metal piece 2 into the oscillation coil 1 are illustrated. It appears from these figures that the oscillator of this invention provides the switching characteristic, in which the current i rapidly varies from the value I to a value I, at a distance d, of insertion of the metal piece 2.
  • the current I is an output derived from the oscillator when the AC current V in FIG. 2B is smoothed.
  • the NPN-type transistor 5 can be replaced by a PNP-type transistor, in which case the polarity of the DC source 3 is reversed and the conducting direction of the diode 9 is reversed.
  • FIG. 5 illustrates one example of a proximity switch of this invention, which employs such an oscillator as described above.
  • the terminals 3 and 3 of the DC source 3 are connected through detection resistors 11 and 12 to connection lines 13 and 14 of the oscillator.
  • a smoothing capacitor 15 is connected, and a parallel circuit formed by the coil 1-1 and the resistor 4 is connected in series to the collector-emitter path of a transistor 5.
  • Transistors l6 and 17 form a current amplifier, which amplifies currents flowing in the detecting resistors 11 and 12 and supplies them to a load 18, such as a lamp.
  • the other constructions are the same as those in the circuit of FIG. 1.
  • the current flowing from the terminal 3 of DC source is divided into two: one drives the oscillator and flows in the terminal 3 of the DC source through the resistors 11 and 12, and the other flows in the baseemitter path of the transistor 16 and that of the transistor l7 and then flows to the terminal 3 of the DC source.
  • the current flowing in the transistor 5 is extremely small, so that the current flowing in the resistor 11 is also small. Therefore, a voltage drop across the resistor 12 is small and the sum of a voltage of about 0.6V necessary for flowing the current in the baseemitter path of the transistor 16 and that of about 0.6V necessary for flowing the current in the base-emitter path of the transistor 17, that is, about 1.2V, is not obtained.
  • a preamplifier employing the transistor 16 may be eliminated as shown in FIG. 6. Further, it is also possible to increase the amplifying stages, if necessary.
  • the abscissa is the temperature T"
  • the ordinate is the inserted position P of the metal piece 2.
  • a line I designates the start of oscillation
  • a line II designates the stop of oscillation.
  • a resistor circuit such as a thermistor of positive characteristic can be employed as the 'bias resistor 8 of the transistor 5.
  • the resistance of the bias resistor 8 decreases at the lower temperature region soas to increase the bias action, while a reverse action is caused at the high temperature region. Accordingly, a uniform characteristic shown in FIG. 8 can be obtained, in which curves Ill and IV respectively designate the start position of oscillation and the stop position of oscillation.
  • numerals 1.5, 0.3 and 0.1 are distances in milli-meter.
  • Actual examples of the resistor circuit are shown in FIGS. 9A, A and 11A, in which a resistor 8-1 has a positive temperature coeficient while resistors 8-2, 8-2a and 8-2b are ordinary resistors.
  • FIG. 9A is employed to improve the characteristic of resistance R in the higher temperature range as shown in FIG. 9B.
  • the resistor circuit shown in FIG. 10A is employed to improve the lower temperature range as shown in FIG. 10B.
  • a characteristic shown in FIG. 11B substantially equivalent to a desired characteristic shown by a dotted line can be obtained by a combination circuit shown in FIG. 11A.
  • the oscillationwinding 1 is formed by two air-core coils 1-1 and l-2, as shown in FIG. 12, in the oscillator of the proximity switch constructed as described above, it was observed that where temperature was changed within the range of, for example, 40 to 100 C, the position of the metal piece 2 at which the oscillator was started to oscillation varies about 4mm as indicated by a curve CV in FIG. 15. This is caused by a change in the amplification factor of the transistor 5 due to the temperature change.
  • the amplification factor of the transistor 5 lowers to cause a decrease in the effective degree of coupling between the coils 1-1 and 1-2 and, as a result of this, the oscillator starts its oscillation at a position where the amount of shielding the coils 1-1 and 1-2 from each other by the metal piece 2 is small.
  • cores 1-3 are inserted into the coils 1-1 and l-2 respectively.
  • the curves CV and CV in FIG. 14 are deviation rate of permeability (u) of the cores showing positive and negative temperature coefficients. Since the cores l-0 of negative temperature coefficients are inserted into the coils l-l and 1-2, it is possible that the variation in the position of the metal piece 2 for starting the oscillation is maintained only within about 0.4mm in the temperature range of .-40 to 100 C, as indicated by the curve CV in FIG. 15.
  • FIGS. 16A and 1613 show examples employing bimetals 23, 23-1 and 23-2, in which the coils 1-1 and 1-2 are moved in the directions of the arrows A2, A3 and A4 due to temperature change, thereby to adjust the degree of coupling between the coils in a direction opposite to that of temperature change.
  • the curves CV and CV in FIG. 17 show temperature compensation characteristics of the examples of FIGS. 16A and 168 respectively.
  • a reference t indicates a normal temperature.
  • the temperature compensation may also be effected by using, as the bias resistor 8 of the oscillator, a resistance element 20 such as a thermistor having a negative temperature characteristic.
  • FIGS. 18A, 19A and 20A illustrate examples of the circuit of the resistor 8 respectively comprising a thermistor 20 and an ordinary series resistor 21, a thermistor 20 and an ordinary parallel resistor 22, and a thermistor 20 and the resistors 21 and' 22.
  • FIGS. 18B, 19B and 208 show their compensation characteristics respectively.
  • the curve CV in FIG. 21 shows the characteristic after compensation in the case of using a thermistor only, from which it appears that the variation in the position of the metal piece 2 can be maintained within about 0.6mm in a temperature range of -30 to C.
  • the entire circuit construction can be simplified by omitting an intermediate amplifier, a Schmitt triggercircuit and so on, which are usually required in the latter stage in the case of constructing a proximity switch.
  • the oscillator Since the oscillator has the switching characteristic, it is possible to eliminate the possibility of breakdown of the output or intermediate stage resulting from an increase in the collector loss due to half conduction.
  • the oscillator, the amplifier, and the display section can be positioned apart from one other.
  • the position of the metal piece for starting the oscillation can be maintained substantially constant irrespective of a temperature change.
  • a switching oscillator comprising:
  • a metal piece employed for being inserted into the oscillation winding to change the degree of coupling between first and second parts of the oscillation winding divided thereinto at the middle tap;
  • an oscillation transistor having its emitter-collector path connected between the first and second terminals of the DC source through the first parallel cir cuit, the middle tap being connected to the first terminal of the DC source connected to the first parallel circuit;
  • bias means connected between the first terminal of the DC source and the base of the oscillation transistor
  • a second parallel circuit formed by a second capacitor and a-diode and connected between the base of the oscillation transistor and the second terminal of the DC source; and in which when a predetermined amount of change in the degree of coupling is caused by the movement of the metal piece, switching to an abrupt generation or stop of an alternating current superimposed on the dc current between the terminals of the DC source is performed.
  • connection lines inserted for connecting the first and second terminals of the DC source to the collector-emitter path of the oscillating transistor through at least one detection resistor and the first parallel circuit;
  • amplification means connected to the detection resistor for amplifying a change of a DC current flowing in the detection resistor to apply an amplyfied output to a load.
  • said bias means comprises at least one resistor having a negative temperature coefficient.
  • a switching oscillator in which said oscillation winding comprises two coils each having a core of a negative temperature coefficient.
  • a switching oscillator according to claim 2, in which said oscillation winding comprises two coils associated with means for controlling the degree of coupling between the coils in the opposite polarity to that caused by a temperature change.

Landscapes

  • Engineering & Computer Science (AREA)
  • Power Engineering (AREA)
  • Electronic Switches (AREA)
  • Inductance-Capacitance Distribution Constants And Capacitance-Resistance Oscillators (AREA)
US00373969A 1972-07-05 1973-06-27 Switching oscillator controlled by a moving metal piece Expired - Lifetime US3805185A (en)

Applications Claiming Priority (4)

Application Number Priority Date Filing Date Title
JP6671472A JPS4926759A (de) 1972-07-05 1972-07-05
JP6671572A JPS5141227B2 (de) 1972-07-05 1972-07-05
JP6671672A JPS5211742B2 (de) 1972-07-05 1972-07-05
JP6671372A JPS4925846A (de) 1972-07-05 1972-07-05

Publications (1)

Publication Number Publication Date
US3805185A true US3805185A (en) 1974-04-16

Family

ID=27464756

Family Applications (1)

Application Number Title Priority Date Filing Date
US00373969A Expired - Lifetime US3805185A (en) 1972-07-05 1973-06-27 Switching oscillator controlled by a moving metal piece

Country Status (2)

Country Link
US (1) US3805185A (de)
DE (1) DE2334094B2 (de)

Cited By (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4014308A (en) * 1974-10-03 1977-03-29 Delta Products, Inc. Ignition system and apparatus and method for generating timing signals therefor
US4072926A (en) * 1972-12-30 1978-02-07 The Toyo Rubber Industry Co., Ltd. Tire pressure warning apparatus
US4638262A (en) * 1984-03-09 1987-01-20 Omron Tateisi Electronics Co. Proximity switch with improved response time and antimagnetic field circuitry
US4942372A (en) * 1987-12-01 1990-07-17 Peter Heimlicher Method and circuit for reduction of temperature dependency in an oscillator
EP0479078A2 (de) * 1990-10-04 1992-04-08 Werner Turck GmbH & Co. KG Induktiver Näherungsschalter
US6420882B1 (en) * 1997-04-08 2002-07-16 Sentech Ag Apparatus for capacitive electrical detection
US20080143448A1 (en) * 2005-01-13 2008-06-19 Thomas Kuehn Proximity Switch and Method for Operating a Proximity Switch
US8432157B2 (en) 2010-09-30 2013-04-30 Rockwell Automation Technologies, Inc. Inductive proximity sensor with active circuit to cancel stray fields

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB9823657D0 (en) * 1998-10-30 1998-12-23 Secr Defence Brit Combined oscillator and voltage step-up circuit

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE1058609B (de) * 1958-07-30 1959-06-04 Metrawatt Ag Transistoroszillator fuer induktive Zeigerabgriffeinrichtungen
US3683294A (en) * 1969-02-18 1972-08-08 Frankl & Kirchner Contactless synchronizer, particularly for sewing machines
US3747012A (en) * 1972-09-21 1973-07-17 R Buck Contactless oscillator-type proximity sensor with adjustable hysteresis

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE1058609B (de) * 1958-07-30 1959-06-04 Metrawatt Ag Transistoroszillator fuer induktive Zeigerabgriffeinrichtungen
US3683294A (en) * 1969-02-18 1972-08-08 Frankl & Kirchner Contactless synchronizer, particularly for sewing machines
US3747012A (en) * 1972-09-21 1973-07-17 R Buck Contactless oscillator-type proximity sensor with adjustable hysteresis

Cited By (11)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4072926A (en) * 1972-12-30 1978-02-07 The Toyo Rubber Industry Co., Ltd. Tire pressure warning apparatus
US4014308A (en) * 1974-10-03 1977-03-29 Delta Products, Inc. Ignition system and apparatus and method for generating timing signals therefor
US4638262A (en) * 1984-03-09 1987-01-20 Omron Tateisi Electronics Co. Proximity switch with improved response time and antimagnetic field circuitry
US4942372A (en) * 1987-12-01 1990-07-17 Peter Heimlicher Method and circuit for reduction of temperature dependency in an oscillator
EP0479078A2 (de) * 1990-10-04 1992-04-08 Werner Turck GmbH & Co. KG Induktiver Näherungsschalter
EP0479078A3 (en) * 1990-10-04 1992-05-20 Werner Turck Gmbh & Co. Kg Inductive proximity switch
US5264733A (en) * 1990-10-04 1993-11-23 Werner Turck Gmbh & Co. Kg Inductive proximity switch
US6420882B1 (en) * 1997-04-08 2002-07-16 Sentech Ag Apparatus for capacitive electrical detection
US20080143448A1 (en) * 2005-01-13 2008-06-19 Thomas Kuehn Proximity Switch and Method for Operating a Proximity Switch
US7626466B2 (en) * 2005-01-13 2009-12-01 Pepperl + Fuchs Gmbh Proximity switch and method for operating a proximity switch
US8432157B2 (en) 2010-09-30 2013-04-30 Rockwell Automation Technologies, Inc. Inductive proximity sensor with active circuit to cancel stray fields

Also Published As

Publication number Publication date
DE2334094B2 (de) 1978-08-03
DE2334094A1 (de) 1974-01-24

Similar Documents

Publication Publication Date Title
US2849611A (en) Electrical oscillator circuit
JP2657873B2 (ja) 変位測定用誘導センサ
US4068189A (en) Linear oscillator for proximity sensor
US3805185A (en) Switching oscillator controlled by a moving metal piece
US2847625A (en) Electrical control apparatus
US3295053A (en) Automatic voltage regulator
USRE24678E (en) pinckaers
US3723862A (en) Detector for detecting objects moving through a magnetic field established between coils of an l-c oscillator
US4609882A (en) Oscillator/demodulator circuit arrangement for an inductive proximity switch
US3503007A (en) Controllable oscillator
US2889496A (en) Electrical control apparatus
US3102217A (en) Mechanically rebalanced condition control servosystem
US2745009A (en) High stability transistor oscillator
US2887642A (en) Damped servomotor system
US3116466A (en) Transistorized tuning fork oscillator
US2908829A (en) Control system with stepped output transistor amplifier
US2964693A (en) Current regulator
US3247466A (en) Power converter with relaxation oscillator starting circuit
US3034022A (en) Switching circuits
JPH0551211B2 (de)
US3134940A (en) Regulated voltage converter circuit
US2955213A (en) Transistor amplifier with stepped qutput
US2987682A (en) Measuring apparatus
US3431471A (en) Static time delay relay
US2964717A (en) D. c. to a. c. converter